Reciprocable hydraulic impact motor



March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 $heetsSheet 1INVENTOR. wee/22$ MW March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 Sheets-Shem 219 f TOE/Vi $451 March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 Sheets-Sheet 3March 23, 1954 c. A. BERGMANN 2,672,847

RECIPROCABLE HYDRAULIC IMPACT MOTOR Filed June 10, 1950 4 Sheets-Sheet 41N VEN TOR.

r97 TOE/VEUS.

Patented Mar. 23, 1954 RECIPROCABLE HYDRAULIC IIWPACT MOTOR Carl A.Bergmann, Milwaukee, Wis., assignor, by

mesne assignments, to Le Roi Company, a corporation of DelawareApplication June 10, 1950, Serial No. 167,335

4 Claims.

My present invention relates in general to improvements in hydraulicmachines, and relates more particularly to various improvements in theconstruction and operation of hydraulically actuated reciprocable impactmotors of the type covered generally by my Patent No. 2,512,763, grantedJune 27, 1950.

In my prior patent above identified, I have shown an improvedhydraulically actuated portable impact motor embodying a differentialpiston reciprocable by liquid underlpressure with the aid of a balancedvalve which is rotatable to automatically alternately admit pressureliquid to the opposed piston faces, and a resilient or pneumatic cushionfor storing energy delivered by the piston while travelling in onedirection and for returning the stored power to the piston so as todeliver powerful impact blows when moving in the opposite direction. Therotation of the automatic valve of this prior impact machine waseffected by an auxiliary rotary hydraulic motor driven by liquid underpressure from the same source which supplied actuating liquid to thepiston of the main motor; and the timing of the valve and of thepneumatic cushion was such that pressure liquid was admitted to thesmaller face of the differential piston and was released from theopposite larger face thereof precisely when the cushion attained itsmaximum power or energy storing position.

While this prior impact assemblage was highly successful and superior toprevious hydraulic hammers in operation, the portable unit wasrelatively bulky and cumbersome to manipulate and the construction ofthe hammer employing a double acting piston and the location of therotary automatic control valve made it rather difiicult to insureaccurate timing and also introduced complications in production andassembly of parts. Thentoo, since these portable impact units areutilized under widely varying temperature conditions which maydetrimentally affect accurate timing and functioning of the controlvalve, the previous device did not make adequate provision forautomatically compensating for such temperature variations in theactuating iquid which travels in a closed circuit, and more than onehammer could not be effectively operated from the same liquid supplysource. In addition to these objections and deficiencies, the priorimpact motors could not be readily actuated to deliver either light orheavy blows at the will of the operator, and since oil is ordinarilyemployed in these hammers no positive provision was made for utilizingescaping oil to best advantage and for preventing messy conditions.

It is therefore a primary object of the present invention to providevarious improvements in the construction and operation of suchreciprocable hydraulic impact motors whereby the structure is materiallysimplified and the functioning thereof is vastly improved.

Another important object of this invention is to provide an improvedportable hydraulically actuated impact unit comprising a reciprocablepower piston and an automatically functioning valve for controlling thedelivery of liquid to and from the piston, wherein the control valve isformed and disposed to produce impact blows of maximum intensity andwith minimum vibration of the unit.

A further important object of the invention is to provide a light butpowerful reciprocable impact motor comprising relatively few simple, andcompact and durable parts which may be quickly and convenientlyassembled or dismantled, and which function automatically with utmostprecision and dependability.

Still another object of my invention is to provide an improved hydraulicimpact assemblage in which the temperature of the power trans mittingliquid may be effectively automatically controlled to insure uniformspeed and most efficient operation of the system, and which is readilyoperable to deliver either light or heavy blows or impacts of anydesired intensity.

An additional object of the present invention is to provide an improvedoil actuated impact motor wherein leakage liquid is prevented frommessing the exterior of the unit, and may be utilized to lubricatevarious parts of the equipment.

Another object of my present invention is to provide an improvedportable hydraulically actuated powerful impact tooland system, which issimpler and less expensive than that shown in my prior patent, and inwhich several hammers may be effectively operated from a common closedfluid supply circuit.

These and other objects and advantages of the present invention will beapparent from the following description.

A clear conception of the several features involved in my presentimprovement, and of the construction and operation of a typical portablehydro-pneumatic hammer embodying the invention, may be had by referringto the drawings accompanying and forming a part of this specificationwherein like reference characters designate the same or similar parts inthe various views.

I Fig. 1 is a longitudinal central section through one of the improved.reciprocable hydraulic impact motors and its resilient pneumaticcushioning device, showing the difierential piston and the cushioningplunger in impact delivery position in solid lines and the latter in itsopposite extreme. 99$?! g9 ,3' 'q-?! .193%

Fig. 2 a side elevation of the portable power unit shown in Fig. 1looking toward one of the air filters for the pneumatic cushioningdevice;

Fig. 3 is an enlarged transverse section through the rotary automaticliquid flow central valve of the unit, taken along the line 3-3 of Fig.i and showing the valve in piston up-stroke position;

Fig. 4 is a similarly enlarged transverse section through the rotaryautomatic liquid flow control valve, also taken along the line 3.73 ofFig. l but showing the valve in piston, downstroke or impact deliveryposition; v Fig. 5 is a likewise enlarged transverse section through therecipro'cable power unit taken along the line 55 of Fig. 1;-

Fig. 6 is a somewhat more enlarged transverse section through thethermostatic control device for the valve impelling rotary. motor of theim: proved impact assemblage, taken along the line 6-5 of Fig. 1 andshowing the automatic temperature actuated motor speed control;

Fig. '7 is an enlarged central vertical section through the manuallyactuated liquid flow regu lating valve of the type. shown in Fig. l, butshowing this valve set for delivery oflight blows;

Fig. 8 is a likewise. enlarged central vertical section through amodified type of manually 3.0? tuated liquid flow regulating valve,likewise show,- ing the sameset for. light blows; and

Fig. 9. is a partially exploded diagram showing a typical liquidsupplyand; circulating system for actuating and controlling the. liquidflow.

The gist of my present invention is the provie sion of a compact butpowerfulv hY-dI'QnPHGUIH8tiC hammer having an impact deliver-y pistoncooperating withv a pneumatic blow: augmenting cushion and provided withdifierential opposite faces the smaller ofwhich is. constantly exposedto. pressure liquidv from. a closed; circulatqry system while thelargeris alternately exposable to fresh pressure. liquid from thesupply.- system together with pressure liquid from the smaller faceduring impactstrokesand toexhaust, during the. return strokes, and: asimple constan tating automatically functioning valve. disposed coaxia vf the power piston. for controllin the now. of" liquid to andfrom. the.piston, races; so; as o produ impa t. blows. or maximu n n ty withoutintroducing excessive vibration the liquid circulating system. theinvention has been s cw b way or illustration as. bein adrantaec uslrappl cable. to. a. univcr a umovable portable hammer. employing. oil as;the acma i g quid: and. havin the control va u onerable by a rotaryhydraulic motor. it; iSgILOtr the nt nt-ta h i b un cqcssar lr res cttheutili y oi the mprov d f atures; a i is a so. colem: plated thatspecific descriptive terms employed e e n e iv n they r ad t. nossib ntep tat c c cntwitnthe disclosure.

Referring to. the drawi gs, the. typical portable hydro-pneumatic.hammer shown therein oomprisesinv general a compositeelongated-maincasing consisting of: alincd, andcoaxial; sections- H), H, l2, I3, I54?firmly. but detachablyinter-connected by. bolts [Sanctcompressionsprings t6; a hydraulic power piston l'l reciprocable within a or .8fame n a. whale: sl eve '9; metered centrally within thev casing sectionH and having a large impact or upper face and a smaller annularretracting or lower face 2i surrounding its piston rod 22; a singleautomatic annular rotary liquid flow control valve 23 journalled in thecasing section I I in axial alignment with the b e, 8 nd b n s an l rtatab by a tary hydraulic motor 24 housed within the casing section [0;a manually operable flow regulating valve 25 slidably confined within ahousing 2Q secured to the casing section II and being operable by meansof a lever 21 and an arm 28 pivotally associated with one of the hammermanipulating handles 29 which are formed integral with the casingsection [0; a pneumatic cushioning plunger 30 slidably confined within abore termed the casing section l2 and being flexibly secured to the mainpiston rod 22; an impact transmitting plug 3| slidably confined within acentral bore formed in the casing section l3-,and projecting. into. thepath of travel of the plunger 30 and an impact. tool or implement, 3-2detachably and slidably confined Within the casing section l4 inalinement with the pl L The upper casing section I0 is formed as, a capsnugly embracing the upper portion of; thecylinder section II andlikewise, embracing a partition 33 which segregates the automaticcontrol valve 23 from its propellin motor 24. The single annular valve23. is adapted o c ns ant r tated at high speed by the rotor ofqthehydraulic motor 24 through a shaft. 34- journalled in the partition 33,and the valve. 2.3 1815. a. pair of diametrically opposed radial ports35 which are inwardly in open communication with the larger upper face20- of the power piston I], and this valve must be. totally balanced atall times. The control valve23 is rotatable. within a stationary bushing36 secured to the casing section II and having therein two accuratelyformed sets of opposed passages, 38 of which the passages 31 are. ofless circumferential width than the passages 38. and the. formercommunicate with high pressure liquid conduits 38 while the latter;-like.- wise communicate with the low pressure conduits 40, seeEigs. 1,3'and4.

In. order to effectively.- balance the pressures acting upon the valve23-, the opposite end surfaces of this. valve are constantly; connectedto the valve ,interior and to the upper piston displacement chamberthrough openings 43, as shown in Fig. l. The cylinder sleeve I 9 isfixedly secured to the casing section H. and in orderto prevent.dangerously; high pressures in the upper cylinder chamber, thevupperextremity of the sleeve t9; isprovided; with cut-outs whichcommunicate with the high pressure conduits 39 past spring pressed; ballrelief-- valves. 42; as shown in Fig. 5.

hiquid underpressure. is; normallyadmitted to the. valve driving motor24, from the high pressure conduits; 31% through a. duct 45; and spentliquid is: exhausted: from, the rotor of the motor 21 through. aduct4.6; and in order to maintain the speed of; the auxiiiarymotorrotorconstant it is. necessary to retaintheflow of propelling liquidsutlicient to; maintain the. desired speed. Since 0 2 rir ie iebly t l mas t actuatin liquid. this. oil out and fiowmore readily when warm; whencold... and the temperature of the. liquid delivered to the motor 24maytherefore be. utilized toregulate thespeed ofthe motor rotor-either.atthemotor'itself; or atsome other e aliw he, i uid. r ula i g systemssirated: n: E is end- 1a ne d valve 41 is disposed in thehigh pressureinlet duct 45' on the motor 24, and the needle valve 41 is movable inone direction by a bellows 48 surrounded by fluid which is expansiblewhen heated to close the needle, and is positively movable in theopposite direction by a helical compression spring 49 to open theneedle, more or less. When the oil is warm less liquid will pass throughthe motor 24 than when cold, but the bellows 48 and spring willautomatically compensate for variations in temperature or fluency of theoil so as to maintain substantially constant speed of revolution of theautomatic valve 23.

This speed of rotation of the automatic valve 23 may also be controlledby maintaining constant viscosity of the oil in a closed system with theaid of mechanism such as illustrated in Fig. 9 and without utilizing abellows and spring actuated needle valve 41 in the unit itself. In thismodified system, a constant pressure variable delivery pump 50 is drivenby an internal combustion engine 5| having an oil cooler 52 associatedtherewith, and the pump 50 has an intake line 53 communicable withasupply reservoir 54 provided with an inlet pipe 55 and also has aflexible discharge line 56 connected to the high pressure conduits 39 ofthe hydraulic hammer unit. The exhaust pipe 51 of the engine 5| has twobranches 58, 59 one of which passes through the oil 60 within thereservoir 54 and the other of which leads to the atmosphere, and theflow of hot exhaust gases through these branches 58, 59 is controllableby a flap valve 6|. The reservoir inlet pipe 55 also has two branches62, 63 one of which passes through the cooler 52 and the other of whichis flexible and communicates with the exhaust conduits 40 of theportable impact unit, and the flow of liquid through these returnbranches 62, 63 is controllable by another flap valve 64. The flapvalves BI, 54 are movable by a thermostat 65 which is activated by abulb 56 disposed within the oil 60 in the reservoir 54 in a manner to bespecifically explained later on.

The manual regulating valve may be either of two types, and as shown inFigs. 1 and 7, the housing 25 of the manually operable flow shutoff andregulating valve 25 may be secured directly to the side of the casingsection II through an opening in the section II], and the valve 25 whichis located in the high pressure conduit 39 is of the reciprocatingpiston type and is totally balanced by virtue of the fact that itsopposite ends are connected to the low pressure conduit 43 while itsmedial portion is recessed to provide annular opposed faces exposable tothe high pressure conduit 39 only when the valve is opened. Aspreviously indicated, the regulating valve 25 is adapted to be openedmore or less by means of the lever 2! and arm 28, but this valve 25 isconstantly urged toward closed position relative to both the pressureand exhaust lines by a spring 68 coacting with its end remote from thevalve stem 5%. The lever 21 is swingably suspended from the casingsection It! by a pivot it and has a slot cooperable with a pin 1| so asto limit the swinging motion thereof, and the arm is is swingablysuspended within one of the handles 29 by another pivot 12 and coactswith the valve stem 59 and with a horn 13 formed integral with the lever21. The handles 29 may also be provided with suitable gripping coveringsl4 and one of these handles serves to protest the adjacent regulatingvalve assembly. The flow regulating valve 25' of Fig. 8 is differentfrom that shown in Fig. 7, since it connects the conduits 39; 4D witheach other when the hammer is 6 inactive, and this permits freecirculation of the oil 60.

When operating these portable hammer units it is frequently desirablefor the operator to regulate the intensity of the blows delivered to thetool 32 and to be able to deliver light blows when performing certaintypes of work where normal heavy blows might be destructive. In order topermit such operation the valve 25 or 25' is provided with a chamfer 15which enables the operator to gradually increase the intensity of theimpacts when starting, or to maintain light blow intensity by merelyholding the lever 21 down to a limited extent. Such operation will causethe chamfer I5 to throttle the flow of liquid delivered to the piston I!to any desired extent thus resulting in blows of variable intensity.

The piston rod 22 is guided for reciprocation in a sleeve bearing 11confined within the lower end of the casing section I! in axialalinement with the cylinder sleeve I9, and this bearing 11 is lubricatedby leakage oil from the upper cylinder chamber. An annular groove 1'! inthe bearing H communicates with one or more low pressure passages 38through a duct 18, see Fig. 1, and serves to return the leakage oil.Thus, only a small amount of leakage oil is passed for the lubricationof the pneumatic cylinder and other moving parts. The pneumatic plunger30 which is slidably confined within a bore of the casing section 12, isflexibly connected to the lower extremity of the piston rod 22 by meansof a universal joint 19, and this plunger 30 is cooperable with airinlet and exhaust ports to confine and compress air in a cushioningchamber 8| formed between the casing section H and the plunger withinthe upper portion of the section l2 whenever the plunger rises. Theports iii! are communicable with the ambient atmosphere through a pairof air filters 82 removably confined within pockets formed in the casingsection l2 by perforated plates 83 swingably secured to the section l2and which are held in closed position by spring retainers 84. The casingsection is within which the motion transmitting plug 3| is slidablyconfined, has lubricant conducting passages 85' formed therein andcooperating with similar passages in the section i2 for conductingleakage oil 60 from the bearing TI to the plug 3| and implement 32without permitting such oil to escape to the exterior of the main casingbody, and the tool or implement 32 may be det-achably secured to thelowermost casing section I4 by means of a spring pressed latch 85, asillustrated. in Fig. 1.

When the improved hydro-pneumatic impact units have been properlyconstructed and assembled as shown and described, they may be utilizedeither singly or in multiple in connection with systems utilizing eitherconstantly or intermittently operable pumps or other sources of supplywherein the oil is circulated either con stantly or at will. If thehammer units are associated with system embodying a constant pressurevariable delivery pump 5!] as in Fig. 9,

the type of regulating valve 25 shown in Figs. 1, 7 and 9 should beutilized, and with this type of valve 25 the flow of oil 50 through thflexible pipes 56, 63 will be interrupted when the corresponding unit isnot in use and the lever 21! thereof is released. However, if a constantliquid delivery is utilized, a modified flow regulating valve of thetype shown in Fig. 8 should be employed, and this valve 25 will permitfree circulation of the oil Bl] through the supply and discharge pipes56, 63ofeachhammer unitwhen. inactive andthe lever 21 thereof isreleased.

Ineither case,.when the lever 21 of a portable hammer is depressed,liquid under high pressure willbe admitted to the conduits 39 of thecorresponding unitand will revolve the rotor of the motor 24' therebyconstantly rotating the balanced automatic; control valve 23 and at highspeed, and liquid under high pressure is always admitted to the lowersmaller face 2-! of the differential. power piston 11 as soon as thevalve 25 or 25 is opened. Whenever the rotary control valve. 23 reachesthe position shownin Fig. 3 with the ports communicating with. thelarger or wider passages 38 and. with the low pressure conduits 40, thenthelarger piston face 20 will be exposed. to. exhaust and the high.pressure liquid. constantly acting upon the smaller piston face 2| willmove the piston I1 and the air compression plunger 30 upwardly to causethe, latter to. confine and, compress air within the cushioning chamber81 At the instant when the piston I1 and plunger 30 reach the upper endof their upstroke, the automatic valve 2:3 will have advanced toward theposition shown in Fig. 4 so as-to connect the upper piston face 20 withthe high pressure conduits 539 and with the; upper piston, displacementchamber through the ports 35. and smaller passages 3i; whereupon thehigh pressure liquid will cooperate with the pneumatic energy. storedwithin the chamber 8 I-, to cause the plunger 30 to deliver a sharpimpact blow to the implement 32 through the plug. 3!.

This cycle, of. operations will be rapidly repeated during, continuedrotation of the valve 23,. and the liquid Eli-will flow constantly inthe same direction through. the; conduits 39, 4E as long as theregulating valve 25 is held in open position; and by properlymanipulating the valve 25- as above described the hammer unit may becaused to delivereither light or heavy blows to the-tool 3 2. If theautomatic speed control for the auxiliary v-alve driving motor 24 shownin Figs; 11 and 6 is utilized, the: fluid coacting with the bellows 48will. adjustv the needle valve 41 in: accordancewi-th variations in thetemperature of theoil Gil-flowing through the motor 24 so as to'maintainthe motor speed substantially constant, and this speed regulating devicemay be utilized in conjunction with any type of liquid circulation butdoes not necessarily affect the viscosityor fluency of the oilby heatingor cooling the same.

However, the speed of the hammers may also be regulated by maintainingconstant viscosity of the actuating liquid and, by utilizingv a systemsuch as shown: Fig. 9 whereby the oil: may be either. heated or cooledto suit. In this automaticviscosity control.system,.the constantpressure.- variable delivery pump 50 may simultaneously operate onev ormore impact units past regulating, valves 25, and the flap valves El, 64willbe automatically adjustedby the thermostat 65 to cause. more. or.less. cooling or heating of the liquid. Whenthe 011,611, in. the powersystem is hot and. highly fluent, the; valve 6] will. be positioned asshownin solid lines to cause the hot engine exhaust gases to escapedirectly to the atmosphere through. the branch pipe 59", and the othervalve 63 will be positioned as shown in dotand-dash. lines. to. cause,the oil. returning, from the-impact unit. to,. travel.- through; the.cooler 52 and. to; become fluent; Iii-the. b11160, too cold. anctnot.sufficiently. flu ntr trie'gvawe 5 I will 8. be positioned as-shown indot-and-dash lines and the other valve 63 will be positioned as' shownin solid lines, thereby causing the cooler 5'2 to be out out and. theexhaust from the engine 5| to travel through the branch pipe 58, thusheatingthe liquid and increasing its fluency. This improved systemtherefore functions toautomatically' control the viscosity of the oil soas to'maintain constant speedof the motor 23, thus providing greatflexibility in operation of the" hammers and effective functioningthereof in hot and cold regions.

From the foregoing detailed description of the construction andoperation of my improved reciprocabl'e impact motor and system, itshould be apparent that I have" in fact provided a hydro-pneumatichammer unit which is simple, compact and durable in construction, andwhich is moreover highly efficient in use and flexible in itsadaptations. The unit embodies onlya single simple automatic valve 23'and a single simple manual flow' regulating valve 25 in order to actuatethe same so as to produce impacts of desired intensity desirable forperforming various classes of work, and by locating the'motor 24', valve23, piston l1, plunger 30 and plugti in axial alinement within axiallyseparable and al'ined casing sections, all of these parts may be quicklyand conveniently assembled or dismantled for inspection. The annularvalve 23 and its confining bushing 36- may be accurately machined so asto opera-tewith utmost precision in producing maximum blows; and bycausing the oil 6'5) to constantly flow in the same direction througheach' portable unit, vibration is reduced to a minimum and annoyance tothe operators is minimized.

The speed of the motor 24 can be selected or set manually with the aidof the needle valve 41, and is maintained by the thermostat 65. Thisreduces the manipulators effort to a minimum. The use of the valve 25'permits any desired numbers of the individual units to be operated byasingle constant pressure, variable delivery pump,

while valve25" is preferably used in conjunction with constant deliverypumps f'orunits requiring only one hammer. The present improved unitsaretherefore entirely automaticin operation except for the actuation of thestarting and stopping'lever 21; and may be effectively operated inextremelyhot or coldweather; All valves are'not only accurately timedbut are also automatically balanced, and'escaping oil is also utilizedto advantage-for lubrication purposes. The improved portableunits may'bemanufactured at moderate cost in various sizes for diverse uses, and arecapable of delivering powerful impacts considering their compactness;

It should be understood that it is, not desired to limit this inventionto the exact details of construction or to theprecisemode of operationof the typical hydraulic impact units herein shown and described, forvarious. modifications within. the. scope of the appended claims mayoccur. topersons skilled inthe art;

I claim:

1'. In a hydraulicallyactuatedxreciproeablaimr pact motor, acasingqhaving a bore; a piston reciprocablewithin said bore and havingopposed facesex-posable to'liquid under pressure, a rotary valveassociatedwith-saidcasing and being automaticallyoperableito-admit saidliquid to saidpiston faces, arotary. motor. operable. by the pres.-sure, .liquidtor actuatesaid valve; and. a thermastatoperablaby;variations inithetemperature. of

9 said liquid admitted to the piston through said valve forautomatically varying the speed of rotation of the valve by regulatingthe speed of said motor.

2. In a hydraulically actuated reciprocable impact motor, a casinghaving a bore, a piston reciprocable within said bore and havingdifferential opposed faces exposable to liquid under pressure, a valveassociated with said casing and being automatically rotatable about theaxis of said piston to admit said pressure liquid to the opposed pistonfaces and from the smaller to the larger face, a rotary motor operableby said liquid to rotate said valve, and a thermostat operable byvariations in the temperature of said liquid for passing through saidvalve for automatically regulating the speed of said motor in accordancewith variations in the viscosity of the liquid.

3. In a hydraulically actuated reciprocable impact motor, a casinghaving a bore, a piston reciprocable within said bore and. havingdifferential opposed faces the smaller of which is constantly exposedand the larger of which is alternately exposable to liquid underpressure, a rotary'valve associated with said casing and beingautomatically rotatable about the piston axis to admit said liquid tothe opposed piston faces, a rotary motor operable by said pressureliquid to rotate said valve, a thermostat operable by variations intemperature of the liquid passing through said valve for maintaininguniform selected speed of said motor and reciprocation of the piston,and means for manually regulating the flow of liquid to said automaticvalve to vary the selected speed of movement and the intensity f" of theimpacts delivered by said piston.

4. In a hydraulically actuated reciprocable impact motor, a casinghaving a bore, a piston reciprocable within said bore and having opposedfaces one of which is alternately exposable to liquid under pressure andto exhaust while the other is constantly exposable to said pressureliquid, a rotary valve associated with said casing beyond one end ofsaid piston and being rotatable to admit liquid under pressure to bothof said faces and to alternately exhaust said one face, a rotary motoroperable by said pressure liquid to constantly rotate said valve, and athermostatically controlled valve confined within said casing and beingoperable by variations in the temperature of the liquid admitted to saidpiston past said rotary valve to automatically vary the speed ofrotation of said motor.

CARL A. BERGMANN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 320,293 Saunders June 16, 1885 660,434 Herzler et a1. Oct. 23,1900 1,087,799 Massey et a1 Feb. 17, 1914 1,104,946 Wilhelm July 28,1914 1,558,221 Bayles et al. Oct. 20, 1925 2,166,940 Conradson July 25,1939 2,512,763 Bergmann June 27, 1950 FOREIGN PATENTS Number CountryDate 501,146 Great Britain Aug. 26, 1938.

